TTC#2 when first child turns 2?

I have a 20-month-old, and my husband and I are currently planning to start trying for a second child when he turns 2. But I've gone back and forth so much on the age gap and timeline! I keep reading that 3.5-year age gaps are great, so then I wonder if we should wait a few more months. But you never know how long it will take etc. etc. So many pros and cons!

I'll add that we're both in our early 30s and only want two kids. Also our son has a fairly significant speech delay at this point (just now starting to say a couple actual words), which might still be a factor when he has a sibling. Hard to know how he'll develop in the next year though.

So, does anyone have experience starting to TTC#2 when their first turned 2? How'd it go? Do you wish you'd waited longer?